1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_ALTERNATIVE_H
3 #define _ASM_X86_ALTERNATIVE_H
4
5 #include <linux/types.h>
6 #include <linux/stringify.h>
7 #include <asm/asm.h>
8
9 #define ALT_FLAGS_SHIFT 16
10
11 #define ALT_FLAG_NOT (1 << 0)
12 #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
13 #define ALT_FLAG_DIRECT_CALL (1 << 1)
14 #define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
15 #define ALT_CALL_ALWAYS ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)
16
17 #ifndef __ASSEMBLY__
18
19 #include <linux/stddef.h>
20
21 /*
22 * Alternative inline assembly for SMP.
23 *
24 * The LOCK_PREFIX macro defined here replaces the LOCK and
25 * LOCK_PREFIX macros used everywhere in the source tree.
26 *
27 * SMP alternatives use the same data structures as the other
28 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
29 * UP system running a SMP kernel. The existing apply_alternatives()
30 * works fine for patching a SMP kernel for UP.
31 *
32 * The SMP alternative tables can be kept after boot and contain both
33 * UP and SMP versions of the instructions to allow switching back to
34 * SMP at runtime, when hotplugging in a new CPU, which is especially
35 * useful in virtualized environments.
36 *
37 * The very common lock prefix is handled as special case in a
38 * separate table which is a pure address list without replacement ptr
39 * and size information. That keeps the table sizes small.
40 */
41
42 #ifdef CONFIG_SMP
43 #define LOCK_PREFIX_HERE \
44 ".pushsection .smp_locks,\"a\"\n" \
45 ".balign 4\n" \
46 ".long 671f - .\n" /* offset */ \
47 ".popsection\n" \
48 "671:"
49
50 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
51
52 #else /* ! CONFIG_SMP */
53 #define LOCK_PREFIX_HERE ""
54 #define LOCK_PREFIX ""
55 #endif
56
57 /*
58 * objtool annotation to ignore the alternatives and only consider the original
59 * instruction(s).
60 */
61 #define ANNOTATE_IGNORE_ALTERNATIVE \
62 "999:\n\t" \
63 ".pushsection .discard.ignore_alts\n\t" \
64 ".long 999b\n\t" \
65 ".popsection\n\t"
66
67 /*
68 * The patching flags are part of the upper bits of the @ft_flags parameter when
69 * specifying them. The split is currently like this:
70 *
71 * [31... flags ...16][15... CPUID feature bit ...0]
72 *
73 * but since this is all hidden in the macros argument being split, those fields can be
74 * extended in the future to fit in a u64 or however the need arises.
75 */
76 struct alt_instr {
77 s32 instr_offset; /* original instruction */
78 s32 repl_offset; /* offset to replacement instruction */
79
80 union {
81 struct {
82 u32 cpuid: 16; /* CPUID bit set for replacement */
83 u32 flags: 16; /* patching control flags */
84 };
85 u32 ft_flags;
86 };
87
88 u8 instrlen; /* length of original instruction */
89 u8 replacementlen; /* length of new instruction */
90 } __packed;
91
92 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
93
94 /*
95 * Debug flag that can be tested to see whether alternative
96 * instructions were patched in already:
97 */
98 extern int alternatives_patched;
99
100 extern void alternative_instructions(void);
101 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
102 extern void apply_retpolines(s32 *start, s32 *end);
103 extern void apply_returns(s32 *start, s32 *end);
104 extern void apply_seal_endbr(s32 *start, s32 *end);
105 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
106 s32 *start_cfi, s32 *end_cfi);
107
108 struct module;
109
110 struct callthunk_sites {
111 s32 *call_start, *call_end;
112 struct alt_instr *alt_start, *alt_end;
113 };
114
115 #ifdef CONFIG_CALL_THUNKS
116 extern void callthunks_patch_builtin_calls(void);
117 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
118 struct module *mod);
119 extern void *callthunks_translate_call_dest(void *dest);
120 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip);
121 #else
122 static __always_inline void callthunks_patch_builtin_calls(void) {}
123 static __always_inline void
124 callthunks_patch_module_calls(struct callthunk_sites *sites,
125 struct module *mod) {}
126 static __always_inline void *callthunks_translate_call_dest(void *dest)
127 {
128 return dest;
129 }
130 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
131 void *func, void *ip)
132 {
133 return 0;
134 }
135 #endif
136
137 #ifdef CONFIG_SMP
138 extern void alternatives_smp_module_add(struct module *mod, char *name,
139 void *locks, void *locks_end,
140 void *text, void *text_end);
141 extern void alternatives_smp_module_del(struct module *mod);
142 extern void alternatives_enable_smp(void);
143 extern int alternatives_text_reserved(void *start, void *end);
144 extern bool skip_smp_alternatives;
145 #else
146 static inline void alternatives_smp_module_add(struct module *mod, char *name,
147 void *locks, void *locks_end,
148 void *text, void *text_end) {}
149 static inline void alternatives_smp_module_del(struct module *mod) {}
150 static inline void alternatives_enable_smp(void) {}
151 static inline int alternatives_text_reserved(void *start, void *end)
152 {
153 return 0;
154 }
155 #endif /* CONFIG_SMP */
156
157 #define ALT_CALL_INSTR "call BUG_func"
158
159 #define alt_slen "772b-771b"
160 #define alt_total_slen "773b-771b"
161 #define alt_rlen "775f-774f"
162
163 #define OLDINSTR(oldinstr) \
164 "# ALT: oldinstr\n" \
165 "771:\n\t" oldinstr "\n772:\n" \
166 "# ALT: padding\n" \
167 ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \
168 "((" alt_rlen ")-(" alt_slen ")),0x90\n" \
169 "773:\n"
170
171 #define ALTINSTR_ENTRY(ft_flags) \
172 ".pushsection .altinstructions,\"a\"\n" \
173 " .long 771b - .\n" /* label */ \
174 " .long 774f - .\n" /* new instruction */ \
175 " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
176 " .byte " alt_total_slen "\n" /* source len */ \
177 " .byte " alt_rlen "\n" /* replacement len */ \
178 ".popsection\n"
179
180 #define ALTINSTR_REPLACEMENT(newinstr) /* replacement */ \
181 ".pushsection .altinstr_replacement, \"ax\"\n" \
182 "# ALT: replacement\n" \
183 "774:\n\t" newinstr "\n775:\n" \
184 ".popsection\n"
185
186 /* alternative assembly primitive: */
187 #define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
188 OLDINSTR(oldinstr) \
189 ALTINSTR_ENTRY(ft_flags) \
190 ALTINSTR_REPLACEMENT(newinstr)
191
192 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
193 ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2)
194
195 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
196 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
197 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags)
198
199 #define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
200 newinstr3, ft_flags3) \
201 ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
202 newinstr3, ft_flags3)
203
204 /*
205 * Alternative instructions for different CPU types or capabilities.
206 *
207 * This allows to use optimized instructions even on generic binary
208 * kernels.
209 *
210 * length of oldinstr must be longer or equal the length of newinstr
211 * It can be padded with nops as needed.
212 *
213 * For non barrier like inlines please define new variants
214 * without volatile and memory clobber.
215 */
216 #define alternative(oldinstr, newinstr, ft_flags) \
217 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
218
219 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
220 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
221
222 /*
223 * Alternative inline assembly with input.
224 *
225 * Peculiarities:
226 * No memory clobber here.
227 * Argument numbers start with 1.
228 * Leaving an unused argument 0 to keep API compatibility.
229 */
230 #define alternative_input(oldinstr, newinstr, ft_flags, input...) \
231 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
232 : : "i" (0), ## input)
233
234 /* Like alternative_input, but with a single output argument */
235 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \
236 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
237 : output : "i" (0), ## input)
238
239 /*
240 * Like alternative_io, but for replacing a direct call with another one.
241 *
242 * Use the %c operand modifier which is the generic way to print a bare
243 * constant expression with all syntax-specific punctuation omitted. %P
244 * is the x86-specific variant which can handle constants too, for
245 * historical reasons, but it should be used primarily for PIC
246 * references: i.e., if used for a function, it would add the PLT
247 * suffix.
248 */
249 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...) \
250 asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
251 : ALT_OUTPUT_SP(output) \
252 : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
253
254 /*
255 * Like alternative_call, but there are two features and respective functions.
256 * If CPU has feature2, function2 is used.
257 * Otherwise, if CPU has feature1, function1 is used.
258 * Otherwise, old function is used.
259 */
260 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
261 output, input...) \
262 asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
263 "call %c[new2]", ft_flags2) \
264 : ALT_OUTPUT_SP(output) \
265 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
266 [new2] "i" (newfunc2), ## input)
267
268 /*
269 * use this macro(s) if you need more than one output parameter
270 * in alternative_io
271 */
272 #define ASM_OUTPUT2(a...) a
273
274 /*
275 * use this macro if you need clobbers but no inputs in
276 * alternative_{input,io,call}()
277 */
278 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
279
280 #define ALT_OUTPUT_SP(...) ASM_CALL_CONSTRAINT, ## __VA_ARGS__
281
282 /* Macro for creating assembler functions avoiding any C magic. */
283 #define DEFINE_ASM_FUNC(func, instr, sec) \
284 asm (".pushsection " #sec ", \"ax\"\n" \
285 ".global " #func "\n\t" \
286 ".type " #func ", @function\n\t" \
287 ASM_FUNC_ALIGN "\n" \
288 #func ":\n\t" \
289 ASM_ENDBR \
290 instr "\n\t" \
291 ASM_RET \
292 ".size " #func ", . - " #func "\n\t" \
293 ".popsection")
294
295 void BUG_func(void);
296 void nop_func(void);
297
298 #else /* __ASSEMBLY__ */
299
300 #ifdef CONFIG_SMP
301 .macro LOCK_PREFIX
302 672: lock
303 .pushsection .smp_locks,"a"
304 .balign 4
305 .long 672b - .
306 .popsection
307 .endm
308 #else
309 .macro LOCK_PREFIX
310 .endm
311 #endif
312
313 /*
314 * objtool annotation to ignore the alternatives and only consider the original
315 * instruction(s).
316 */
317 .macro ANNOTATE_IGNORE_ALTERNATIVE
318 .Lannotate_\@:
319 .pushsection .discard.ignore_alts
320 .long .Lannotate_\@
321 .popsection
322 .endm
323
324 /*
325 * Issue one struct alt_instr descriptor entry (need to put it into
326 * the section .altinstructions, see below). This entry contains
327 * enough information for the alternatives patching code to patch an
328 * instruction. See apply_alternatives().
329 */
330 .macro altinstr_entry orig alt ft_flags orig_len alt_len
331 .long \orig - .
332 .long \alt - .
333 .4byte \ft_flags
334 .byte \orig_len
335 .byte \alt_len
336 .endm
337
338 .macro ALT_CALL_INSTR
339 call BUG_func
340 .endm
341
342 /*
343 * Define an alternative between two instructions. If @feature is
344 * present, early code in apply_alternatives() replaces @oldinstr with
345 * @newinstr. ".skip" directive takes care of proper instruction padding
346 * in case @newinstr is longer than @oldinstr.
347 */
348 #define __ALTERNATIVE(oldinst, newinst, flag) \
349 740: \
350 oldinst ; \
351 741: \
352 .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\
353 742: \
354 .pushsection .altinstructions,"a" ; \
355 altinstr_entry 740b,743f,flag,742b-740b,744f-743f ; \
356 .popsection ; \
357 .pushsection .altinstr_replacement,"ax" ; \
358 743: \
359 newinst ; \
360 744: \
361 .popsection ;
362
363 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
364 __ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
365 .endm
366
367 #define old_len 141b-140b
368 #define new_len1 144f-143f
369 #define new_len2 145f-144f
370 #define new_len3 146f-145f
371
372 /*
373 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
374 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
375 * @feature2, it replaces @oldinstr with @feature2.
376 */
377 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
378 __ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
379 \newinstr2, \ft_flags2)
380 .endm
381
382 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
383 __ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
384 \newinstr3, \ft_flags3)
385 .endm
386
387 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
388 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
389 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
390 newinstr_yes, ft_flags
391
392 #endif /* __ASSEMBLY__ */
393
394 #endif /* _ASM_X86_ALTERNATIVE_H */
395
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